JP4230593B2 - Pneumatic tires for motorcycles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire for a motorcycle, and at the time of a limit turning operation in which the camber angle imparted to the tire is increased to the limit, still produces a large side force and exhibits excellent road surface grip performance. The stability is advantageously improved.
[0002]
[Prior art]
For conventional motorcycles in which a pair of sidewall portions extending radially inward are provided on both sides of a tread portion that extends in an arc shape up to the maximum width position of the tire, and a bead portion is provided at the radially inner end of each sidewall portion. In a pneumatic tire, a side edge of a belt that is located on the inner peripheral side of a tread portion and reinforces the tire is generally located on the tire equatorial plane side with respect to a normal line standing at the tread end.
[0003]
[Problems to be solved by the invention]
When turning a motorcycle, the camber thrust generated according to the magnitude of the camber angle is tilted to the inside of the turn to give the camber angle, the side force as a force against the centrifugal force. In pneumatic tires for motorcycles, the tread portion extends in a circular arc shape from the center vertex position to the position forming the maximum width of the tire in the cross section in the width direction of the tire. Even if the contact area of the tread gradually shifts to the tread end side as the camber angle increases, a sufficiently large contact area is secured under a substantially constant contact surface shape.
[0004]
By the way, in such a pneumatic tire for a motorcycle in which the tread portion extends in an arc shape with a relatively small radius of curvature within the cross section in the tire width direction, the contact area of the tread portion is deformed to a flat shape. As a result, the belt portion located corresponding to the contact area is mainly subjected to compressive strain in the tire circumferential direction, and therefore the belt cannot hold tension and the belt. Stiffness will decrease.
[0005]
In response to such a decrease in belt rigidity, when the tread portion comes into contact with the central portion in the width direction or in the vicinity thereof, the belt portions positioned corresponding to the tread portions existing on both sides of the contact area are separated. Since high rigidity is exhibited under the action of a large tension, sufficient rigidity in the tire width direction can be ensured based on sufficient effects, and therefore excellent steering stability can be exhibited.
[0006]
However, as the camber angle increases, the tread portion contacts the tread end or the vicinity thereof, so that when the belt portion that receives the compressive strain in the tire circumferential direction reaches the belt side edge, Even if there is a high-rigidity belt part on the tire equator side, there will be no high-rigidity belt part on the opposite side, ensuring sufficient rigidity in the tire width direction. Insufficient rigidity prevents the camber thrust from being sufficiently increased, and the steering stability performance is impaired.
[0007]
And this is because, unlike the conventional tire, the belt side edge is positioned before the camber angle is increased to its limit value by positioning the belt side edge on the tire equatorial plane side with respect to the normal line standing at the tread end. Is particularly serious when the tire is subjected to circumferential compressive strain, and in such a tire, the steering stability is greatly impaired in the limit turning traveling in which the camber angle is increased to the limit value.
[0008]
An object of the present invention is to solve such problems of the prior art, and the object of the present invention is to increase the camber angle to its limit, and still to both sides of the tread area. In addition, the presence of a belt portion that maintains sufficiently large circumferential tension without being subjected to circumferential compressive strain ensures that large side forces are generated and that excellent road surface grip performance is exhibited, thereby improving steering stability. The object is to provide a pneumatic tire for motorcycles that is effectively improved.
[0009]
[Means for Solving the Problems]
A pneumatic tire for a motorcycle according to the present invention is provided with a carcass that extends in a toroidal manner between a pair of bead cores, and whose side portion is folded around the bead core and wound up radially outward. A belt is disposed on the outer peripheral side, and a tread portion that extends in an arc shape and specifies the maximum width of the tire is provided on the outer peripheral side of the belt, and a pair that extends radially inward on both sides of the tread portion. In addition, the belt extends in a direction intersecting the tire equatorial plane when a bead portion including a bead core is continuously provided at the radially inner end of each sidewall portion. made from two layers of belt layers composed of codes, the side edges of the belt, with is located in the bead portion side from the normal to the tread edge, and side edges of the belt Between notation lines, in which the distance measured along the belt was 3.0～10.0Mm.
[0010]
In this tire, even when the tread part contact area reaches the tread edge due to the increase of the camber angle, the belt part located on the bead side from the normal line is outside the contact area and still has a large circumferential direction. Tension can be maintained, and as a result, each belt part located across the contact area can exhibit high rigidity, so that the tire has a case where the center part in the width direction of the tread part contacts the ground. Similarly, the high rigidity in the width direction can be maintained.
[0011]
Therefore, even in the limit turning with the camber angle increased to its limit, it is possible to generate a large camber thrust, and thus a side force, as well as a high road surface grip force, which advantageously improves steering stability. Can be made.
[0012]
By the way, this becomes even more remarkable when the distance measured along the belt between the side edge of the belt and the normal line is in the range of 3.0 to 10.0 mm.
That is, when the distance is less than 3.0 mm, it is not effective to protrude the belt side portion toward the bead portion side with respect to the normal line, and a sufficiently large tension is held at the belt side edge when applying a large camber angle. On the other hand, if the distance exceeds 10.0 mm, the function of the belt side portion reaches the upper limit value.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on the drawings. FIG. 1 is a cross-sectional view showing an embodiment of the present invention for a half portion of a tire. Here, for example, the radial carcass 2 is configured with at least one carcass ply that extends in a toroidal manner between the pair of bead cores 1 and that each side portion is folded around the bead core 1 and wound outward in the radial direction. On the outer peripheral side of the crown portion of the carcass 2, a belt 3 composed of a two-layer belt layer composed of a plurality of cords extending in a direction intersecting with the tire equatorial plane is disposed.
[0014]
Further, a tread portion 4 extending in an arc shape to the maximum width position of the tire is provided on the outer peripheral side of such a belt 3, and a pair of substantially extended radially inwards on both sides of the tread portion 4. The sidewall portions 5 are provided continuously, and the bead portions 6 including the bead cores 1 are continuously provided at the inner ends of the sidewall portions 5.
[0015]
Further, here, the side edge P of the belt 3 is positioned closer to the bead portion than the normal line 7 standing at the tread end E, and preferably the distance of the side edge P from the normal line 7 measured along the belt 3. Let l be in the range of 3.0-10.0 mm.
[0016]
In the tire configured as described above, even when the tread end E comes into contact with the ground due to an increase in the camber angle imparted to the tire, the belt 3 is positioned closer to the bead portion than the normal line 7. The part is not subject to compressive strain in the circumferential direction, and still maintains a large tension, so that the rigidity in the width direction of the tire is maintained high, and both the camber thrust and the road surface grip force are advantageously improved. Stability can be greatly increased.
[0017]
FIG. 2 shows the tension acting on the belt side edge when a 45 ° camber angle is given to the tire, using the belt side edge position with respect to the normal 7 as a parameter.
According to this, when the belt side edge P is positioned on the tire equatorial plane side with respect to the normal line 7, circumferential compressive strain is generated at the belt side edge P, and the tension becomes a negative value. By projecting the side edge P about 3 mm or more to the bead part side with respect to the normal 7, the belt side edge tension can be set to a positive value, and the side edge tension has a protruding length of 10 mm. It turns out that it increases gradually.
On the other hand, it is also clear that even if the protruding length of the belt side edge P from the normal line 7 exceeds 10 mm, a substantial increase in tension cannot be brought about.
[0018]
FIG. 3 is a graph showing the camberlass in the same case with an exponent value. According to this graph, the camberthlas can be advantageously increased by positioning the belt side edge P closer to the bead part than the normal line 7. It can be seen that the camber lath becomes almost the upper limit when the distance 1 from the normal 7 of the belt side edge P reaches 10 mm.
[0019]
Thus, in this pneumatic tire, by positioning the belt side edge P closer to the bead part side than the normal line 7, a large side force and a high road surface grip force are generated when the camber angle is increased to the limit. Thus, both the maneuverability and the stability can be effectively improved.
[0020]
【Example】
Limit turning when running on a dry test course with tires of size 120 / 70R17 mounted on the front wheels of the motorcycle with various changes in the relative position of the belt side edge P with respect to the normal 7 Each of the handling stability and ride comfort at the time was evaluated by a skilled rider, and the results were as shown in the graph of FIG.
In addition, this feeling evaluation shall show the result which was excellent, so that 10 points were perfect and the score was large.
[0021]
According to FIG. 4, it is clear that the evaluation of steering stability shows almost the same increasing tendency as the camber thrust shown in FIG. 3, and the ride side is that the belt side edge P is separated from the normal 7 by 10 mm or more. Thus, it can be seen that the lowering particularly occurs when the bending rigidity of the sidewall portion becomes too high.
[0022]
【The invention's effect】
As is apparent from the above, according to the present invention, in particular, the belt side edge is positioned within the range of 3.0 to 10.0 mm on the bead side from the normal line standing at the tread end. As a result, even during the limit turning travel in which the camber angle imparted to the tire is increased to the limit, it is possible to ensure the generation of a large side force and a high road surface grip force and to effectively improve the steering stability.
[Brief description of the drawings]
FIG. 1 is a transverse sectional view showing an embodiment of the present invention about a half portion of a tire.
FIG. 2 is a graph showing a relationship between a relative position of a belt side edge and a tension acting thereon.
FIG. 3 is a graph showing a relationship between a relative position of a belt side edge and a generated camber thrust.
FIG. 4 is a graph showing a relationship between a relative position of a belt side edge and an actual vehicle feeling score.
[Explanation of symbols]
1 Bead core 2 Carcass 3 Belt 4 Tread part 5 Side wall part 6 Bead part 7 Normal line E Tread edge P Belt side edge

Claims (1)

A carcass provided to extend toroidally between a pair of bead cores and a belt disposed on the outer peripheral side of the crown portion of the carcass are provided, and the maximum width of the tire is specified by being disposed on the outer peripheral side of the belt. A tread portion, a pair of sidewall portions extending radially inward from both sides of the tread portion, and a bead portion that is provided continuously to the radially inner end of each sidewall portion and encloses the bead core. And
The belt is composed of a two-layer belt layer composed of a plurality of cords extending in a direction intersecting the tire equator plane, and the side edge of the belt is positioned closer to the bead portion than the normal line standing at the tread end, A pneumatic tire for a motorcycle, wherein a distance measured along the belt between the side edge and the normal line is 3.0 to 10.0 mm.

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